Cylinder and piston structures



Feb. 13, 1962 w. c. CHENEY ETAL 3,021,183

CYLINDER AND PISTON STRUCTURES Filed Nov. 2a. 1958 116.4; INVENTORS.

ATTORNEYS.

3,021,183 CYLINDER AND PESTGN STRUCTURES Wendell C. Cheney and HaroldMorehouse, Lake City,

Minn,- and Marshall G. Whitfield, Garden City, l l.Y.g

said Cheney and said Morehouse assignors, by direct and mesneassignments, to Gould-National Batteries,

Inc., St. Paul, Minn, a corporation of Delaware Filed Nov. 28, 1958,Ser. No. 777,036 11 Claims. (Cl. 309-6) This invention relates to theproblem of minimizing wear and scoring of pistons and cylinders,particularly in internal combustion engines, and has also to do withvarious combinations of cylinder and piston structures in which thisgeneral object is attained.

Generic aspects of the invention apply to engines having ferrouscylinders or cylinder blocks, cylinders or cylinder blocks made in partof heavy metal and in part of light metal such as aluminum, cylinders orcylinder blocks made entirely of light metal, and to engines of theso-called wet sleeve type in which a sleeve pro viding the inner surfacewhich coacts with a piston is removably and renewably mounted in a blockand is contacted on its outer surface by a cooling iluid. The inventionis applicable to engines of the above types using ferrous pistons, lightmetal pistons, and composite pisas respects'engine cylinders tons oflight metal containing heavy metal reinforce- "-1 mcnts, the pistonsbeing used with or without rings. The generic aspects of the inventionare further applicable to all types of internal combustion engines, fromsmall structures such as are used to power pumps, lawn mowers,motor-cycles and the like, through normal fourcycle engines such as areused in automotive equipment, to heavy duty structures includingtwo-cycle engines, super-charged diesel engines, and engines in thegasoline and diesel fields using very high compression ratios.

Structures of all of these types are well known to skilled workers inthe art and do not require description. The invention will be explainedin connection with a specific embodiment which is a light metal cylinderor block and a light metal, ringless piston, with incidental referencesto other types of structure, it being understood that the specificembodiment is exemplary only and not limiting, beyond the terms of theappended claims. The exemplary embodiment is chosen because it serves toillustrate certain specific aspects of the invention as well as the moregeneral aspects.

Additional and more specific objects of the invention are:

The provision of a structure facilitating the use of ringless pistons inengine cylinders.

The provision of a structure facilitating the use of light metal pistonsin light metal cylinders.

The provision of a structure facilitating the use of ringless pistons inlight metal cylinders.

These and other objects of the invention which will be set forthhereinafter or will be apparent to one skilled in the art upon readingthese specifications, are accomplished by that structure and arrangementof partsof which the aforesaid exemplary embodiment will now bedescribed. Reference is made to the accompanying drawings wherein:

FIGURE 1 is a longitudinal sectional view of an exemplary cylinder witha piston partially shown therein.

FlGURE 2 is an elevational View of a ringless piston of a type which maybe used in the cylinder of FIG- URE 1.

FIGURE 3 is a diagrammatic view of an engine showing another embodimentof the invention.

FIG. 4 is a diagrammatic view showing a piston and cylinder embodyinganother form of the invention.

3,621,183 Patented Feb. 13, 1962 It is known that wear, abrasion,scoring and scufiing and pistons are influenced by a number of factorssuch as temperature and the nature of the metals which operate againsteach other. Most of the wear of cylinders and cylinder liners ininternal combustion engines occurs in that portion of the cylinder whichlies between the upperand lower limits of travel of the top compressionring of the piston, the cylinder wear being greatest where thecompression ring reverses its direction of travel. Lubrication also hassome effect upon wear; and it has been recognized that wear is minimizedto a certain extent by a porous condition of the inside surface of thecylinder. Porous metals or finishes which, nevertheless, are hard enoughto sustain abrasion, have been found desirable; and attempts have beenmade to accomplish the edect of porosity by an artificial roughening ofthe bore of the cylinder.

- Porosity, whether naturally occurring in the surface of of the metalor whether artificially produced, has not been found a complete solutionfor the problem. As the porosity is relatively slight, the desiredamount of lubrication may not be attained; but if the interior surfaceof the cylinder is roughened or rendered porous to such a degree that ahighly efiective amount of lubrication will be present between thepiston and the cylinder, the consumption of oil by the engine is verygreatly increased, with additional undesirable effects such as cokingand the like.

. The present invention is based on the discovery that wear, abrasion,scuffing, and scoring may be very largely eliminated or amelioratedwithout increasing oil consumption by a construction and procedure whichwill now be described. Referring first to FIGURES l and 2, there isillustrated at 1 an exemplary cylinder for an internal combustionengine. This cylinder is illustrated as of the air-cooled type and hencecharacterized by projecting cooling fins 2. The metallic material ofwhich the cylinder is made is not a limitation upon the aspect of theinvention here under description, nor is the form of the cylinder or itsair-cooled or fluid-cooled character. The particular cylinder is shownas having ports 3, 4, 5 and 6 which, again, are illustrative but notlimiting. A piston 7 operates within the cylinder and comprises a headportion 8 and a skirt portion 9. The piston may have any suitableconstruction and may be made of any suitable metallic material. It willhave the usual pin holes 10 surrounded by interior bosses for thereception of the conventional wrist pins.

It has been found that adequate lubrication may be supplied to thepiston without excessive oil consumption by the provision of aconfiguration in the inner surface of the cylinder wall and the locationof this configuration in a particular way. In its simplest form, theconfiguration consists of a groove 11a formed in the inner cylinderwall. This groove may be and preferably is fully circular. Itsdimensions may vary; but excellent results have been attained with agroove about inch in width having a depth of about the same'dimension.The depth and width of the groove may be substantially varied inaccordance with the lubricant-delivering capacity desired in anyparticular cylinder of any particular size.

Grooves from a few thousandths of an inch in width and depth up togrooves, say, A inch or inch in width and depth, may be employed,depending somewhat on the size of the cylinder and the length of thepiston stroke. But it iswithin the purview of the invention to provide aseries of annular grooves in the interior surface of the cylinder, whichgrooves are closely spaced so that they may be located as hereinaftertaught. If the grooves themselves are very small, there will desirablybe a pluralprovide the required invention, the groove or grooves will beuncovered by the end of the piston ski-rt;

Where the piston has rings, these should not travel over or past thegrooves. The grooves should not be uncovered by the head of the pistonin any position; but in some structures good results can be obtainedeven though the skirt does not uncover or fully uncover the groove orgrooves at the top end of the stroke.

When a groove or grooves are provided and located as herein set forth,and means are provided to deliver oil to the grooves, it will be foundthat the piston is kept in a well lubricated condition with the skirt ofthe piston covered at all times with an ample film of oil, while at thesame time the consumption of oil by the engine will not be significantlyincreased. Thus, the structure of this invention operates unexpectedlyin a way very different from porosity or roughness in the cylindersurface. The delivery of oil to the groove or grooves may beaccomplished by the splashing of oil from the engine crankcase, sincethe groove or grooves will be exposed during each cycle. It does notconstitute a departure from the invention, however, to provide specialmeans for delivering oil to the groove or grooves, such as spray nozzlesor other means involving the use of conduits, if such are desired.

The groove 110, or its equivalent as hereinafter set forth, acts to keepthe skirt of the piston well lubricated. At the same time, the groove isso located that the upper part of the piston, i.e. the portion of thepiston adjacent the head, does not pass the groove, but is alwayslocated on the cylinder head side of the groove, irrespective of theposition of the piston. Consequently, the groove does not act to deliveroil into the firing space of the cylinder. At the same time, oil ismaintained between the piston skirt and the cylinder walls, so thatlubricant in relatively small but suflicient quantities is delivered tothe head end of the piston or to the piston rings, if rings are used. Itis believed that this action largely explains the reason why the meansof this invention are effective in minimizing wear and scoring, whilethey do not significantly increase oil consumption.

FIGURE 2 illustrates a piston without rings. Such pistons mayadvantageously be provided with one or two shallow grooves 11 and 12near the head end, in approximately the position of the piston rings inthe ordinary piston. These help to increase the lubrication at the headend of the piston without pumping oil into the firing space. Adistributor groove 13 may be provided in the skirt end of the piston ifdesired. Grooves on the piston do not act in the same way as the groove11a in the cylinder wall. The groove 11a greatly increases theefficiency and life of ringless pistons in internal combustion engines.

It has already been indicated that a series of grooves may besubstituted for the single groove 11a, providing the grooves are soclosely spaced that they may be located in the span of the travel of thepiston as hereinabove indicated. The lubrication means of this inventionis not restricted to a circular groove or series of grooves. It is wellknown that in most engine cylinders the wear or scoring tendency islocalized in portions of the cylinder walls (and corresponding portionsof the piston) lying substantially normal to the axis of the wrist pin.The groove or grooves may be confined to such portions of the cylinderwalls. In FIGURE 4 there is cally an engine having a horizontal cylinderlq, with piston 15 having rings 16. The piston is connected by usualconnecting rod 17 to a crank shaft 18. If the cyclical operation of theengine is such that the illustrated relationship of parts obtains at thestart of the power stroke, the wear and scoring tendency will be largelylocalized at the top sides of the cylinder wall and piston. In such aninstance it is within the scope of this invention to confine the grooveor grooves 11a to the top side of the cylinder wall as shown. Similarlyin cylinders where the thrust load comes at the bottom side the grooveor grooves may be confined thereto.

7 ing provided with illustrated diagrammati- A result similar to thatproduced by the groove or grooves 11a can be obtained by the use ofother indentations, relatively closely spaced, of sufi'iciently greatcapacity to hold the required amount of lubricant, and confinedlengthwise of the cylinder to such an area of the cylinder wall that,like the grooves, they will be uncovered by the piston skirt when thepiston is in its top or outermost position, but will lie inwardly of thepiston rings on the outer part of the piston when the piston is in itsbottom or innermost position. Such indentations may be produced invarious ways, but are most conveniently made by knurling. In FIGURE 3there is shown a portion of a cylinder wall 19 hearing a series ofindentations 20 formed by knurling.

The grooves 11a or the indentations 20 are formed by the use of acutting tool or knurling tool employed in the process of finishing theinterior of the cylinder.

An essential difference between the action of the means of thisinvention and a general porosity of the interior walls of the cylinderlies in the fact that if a general porosity has enough capacity to keepthe skirt of a piston well lubricated, it will tend to pump oil into thefiring space of the cylinder whereas the means of this invention doesnot. The means of this invention, however, may be used in cylindershaving a degree of porosity without departing from the spirit of theinvention.

As indicated, the means of this invention are of utility in all of theknown types of cylinder and piston combinations. The cylinder may be aircooled and hence provided with heat-dispersing fins, or it may be watercooled and form a part of a cylinder block having an integral coolingjacket. Yet again the cylinder may be of the wet sleeve type in whichthe cylinder proper is a sleeve which is replaceably positioned within acooling jacket. The pistons may be of heavy metal, e.g. cast iron, or oflight metal, e.g. aluminuinor aluminum alloys, or of light metal withheavy metal reinforcements. The pistons may be used with or withoutrings. The means of the invention are elfective despite considerablevariations in piston clearance. For example, in an engine having a castiron cylinder and a cast iron piston, a clearance of .001 inch per inchof cylinder bore is common with a round ground ferrous piston (theclearance being somewhat less when the piston is cam ground), the pistonbe rings. The invention works well with such a clearance. Where lightmetal pistons are employed in ferrous cylinders a clearance of about.00075 inch per inch of cylinder bore is usual, most light metal pistonsbeing cam ground. The present invention is very efiective in minimizingwear and scoring with such a clearance; and where both piston andcylinder are made from the same aluminum alloy closer clearances can beused. Where pistons without rings are employed, closer tolerances atfull operating temperatures are generally sought, a clearance of about.0005 inch per inch of cylinder bore being effective for engines withcylinder bore diameters of around. 2 inches. The means of this inventionnot only serve to maintain full lubrication under all such clearances,but are of great importance in the use of ringless pistons because thelife of such pistons is very considerably prolonged.

The invention is of especial importance not only in the field ofcylinders and pistons made of metals which are matched as tocoelficients of expansion, and where close tolerances are generallysought, but also in the field of cylinders made of light metals. It hasnot generally been found satisfactory to make cylinders of aluminum orordinary hypoeutectic aluminum alloys since their wear resistance is notgreat. The means herein taught, however, will usefully prolong the lifeof such cylinders rendering them useful especially in small engines. Ina copending application of Marshall G. Whitfield and Wendell C. Cheney,two of the present inventors, entitled Aluminum Alloy Engine Cylinder,Serial No. 743,659, filed June 23, 1958, there are described enginecylinders made of or consisting on their inner wall surfaces of ahypereutectic silicon-aluminum alloy containing substantially 17 to 25%or more silicon. Preferred structures may be made in accordance withthat invention by preforming an interior sleeve or cylinder of thehypereutectic alloy and then casting about its outer surfaces at body ofaluminum alloy of diiferent characteristics, permissibly but notnecessarily hypoeutectoid, but having a different coefiicient ofexpansion such that the hypereutectic sleeve is maintained undercompression. Yet again a structure may be made in which a hypereutecticsleeve is located within a block of other light metal and is water orair cooled. Hypereutectic cylinders of this character, used inconnection with matched light metal pistons with or without rings ottera large field of utility for the practice of the present invention. Theprecipitated silicon in the hypereutectic alloy contributes to hardnessand wear resistance. The interior surfaces of such cylinders usuallyhave a slight but useful porous structure. When the principles of thisinvention are applied to such structures, the useful life thereof isvery greatly prolonged; and this invention has permitted the efiectiveuse of matched combinations of light metal cylinders and light metalpistons at close tolerances.

Modifications may be made in the invention without departing from thespirit of it. The invention having been described in certain exemplaryembodiments what is claimed as new and desired to be secured by LettersPatent is:

1. In combination, in an internal combustion engine, a cylinder havingan interior surface, a piston in sliding engagement with said interiorsurface and having a head and a skirt, the interior surface of saidcylinder having an oil-receiving reservoir in the form of at least oneindentation, said reservoir being limited in extent longitudinally ofsaid cylinder to a position at which it will be uncovered by the skirtof said piston at one extreme of the piston travel but covered by saidskirt at the other extreme, the said reservoir having a substantialextent circumferentially of said cylinder.

2. The structure claimed in claim 1 wherein said piston has rings andwherein said reservoir is located in such position that it lies at alltimes on the skirt side of said rings.

3. The structure claimed in claim 2 wherein the interior surface atleast of said cylinder is formed of a hypereutectic silicon aluminumalloy.

4. The structure claimed in claim 1 wherein said piston is devoid ofrings.

5. The structure claimed in claim 4 wherein the interior surface atleast of said cylinder is formed of a hypereutectic silicon aluminumalloy.

6. The structure claimed in claim 4 wherein the interior surface atleast of said cylinder is formed of a hypereutectic silicon aluminumalloy, and in which said piston is formed from a similar hypereutecticsilicon aluminum alloy and has a clearance of about /z thousandths of aninch per inch of cylinder diameter in said cylinder.

7. The structure claimed in claim 1 wherein said oilreceiving reservoircomprises a series of closely spaced indentations, said series extendingat least partially circumferentially of said cylinder.

8. In combination a cylinder and a piston for reciprocation therein,said cylinder having a head end and an interior surface, said pistonhaving a head end and a skirt, said piston being connected with a crankshaft by means of a connecting rod and a wrist pin, and an oilreceivingreservoir in the form of at least one indentation in the interiorsurface of said cylinder so located as to be uncovered by the skirt ofsaid piston at the extremity of the travel of said piston toward thehead end of said cylinder, and so as to fall short of the head end ofsaid piston at the opposite extremity of its travel, said reservoirbeing limited in extent longitudinally of said cylinder being located ina portion of the interior surface of said cylinder opposite a linenormal to the wrist pin of said piston, the said reservoir havingasubstantial extent circumferentially of said cylinder.

9. In combination, in an internal combustion engine, a cylinder havingan interior surface, a piston in sliding engagement with said interiorsurface and having a head and a skirt, the said interior surface of saidcylinder having an oil-receiving reservoir in the form of a grooveextending circumferentially of said interior surface of said cylinder,and so positioned that it will be uncovered by the skirt of said pistonat one extreme of the piston travel, but covered by said piston at theother extreme, the said piston and the interior surface of said cylinderbeing made of metal having substantially the same coefficient ofexpansion.

10. The structure claimed in claim 9 wherein said piston has acircumferential groove in its skirt travelling past the groove in theinterior surface of said cylinder upon each stroke of said piston.

11. The structure claimed in claim 10 wherein said piston and theinterior surface at least of said cylinder are formed from ahypereutectic silicon aluminum alloy.

References Cited in the file of this patent UNiTED STATES PATENTS1,193,200 Strand Aug. 1, 1916 1,295,329 Kennedy Feb. 25, 1919 1,459,819Bonner June 26, 1923 1,871,820 Morton Aug. 6, 1932 FOREIGN PATENTS632,173 Germany Oct. 4, 1932 1,097,144 France Feb. 9, 1955 OTHERREFERENCES Schafer: German application 1,007,560, printed May 2, 1957(K1 46Cl) 2 pages spec, 1 sheet dwg.

